There are three basic types of bulk flow seed or material metering devices: namely the fluted wheel with slide type; the internal force feed type; and the external tooth force feed type. The present invention is particularly applicable to devices of the last-mentioned type.
In present art devices a toothed metering wheel is mounted to a shaft which can be rotated at different rates to provide different rates of material dispensing. Different rates can also be obtained by using "fine" or "coarse" wheels, that is wheels having a large or small number, respectively, of seed receiving pockets about the circumference. Alternatively, a system such as is shown in Canadian Pat. No. 1,103,996 issued June 30, 1981 to Amazonen-Werke H. Dreyer G.m.b.H. & Co. KG could be utilized, that system including a fine wheel and a coarse wheel side by side on the same shaft and couplable together to obtain a different feeding rate. When seeding coarse grains with this system the fine wheel only serves to drive the coarse wheel, playing a very small role in the actual dispensing operation. The operator is also limited in the variety of wheels which are available to seed an even larger variety of seeds since he has no choice beyond the dispensing wheels purchased with his seeder. Furthermore, if a seed wheel is damaged or worn the operater must dismantle a large portion of his machine to replace the offending seed wheel.
It is very desirable to be able to readily change worn or damaged seed wheels and to be able to seed at rates beyond what is available through the machine transmission and/or through the use of presently-available fine/coarse seed wheel combinations.